Semiconductor packages are electronic devices for accommodating active components such as semiconductor chips, whose structure is primarily composed of a chip mounted on a substrate and electrically connected to the substrate via conductive elements such as bonding wires; an encapsulation body is formed by a resin compound (such as epoxy resin, etc.) on the substrate to encapsulate the chip and bonding wires which are protected against external moisture and contaminant. The encapsulation body is usually opaque or non-transparent, thereby making a photosensitive chip such as CMOS (complementary metal oxide semiconductor) chip that requires light for operation not suitably incorporated in such a semiconductor package.
Accordingly, U.S. Pat. No. 6,590,269 provides a semiconductor package with a structurally modified encapsulation body for allowing light to reach the photosensitive chip with reference to FIG. 4. In this semiconductor package, the photosensitive chip 10 is mounted on a substrate 11 and electrically connected to the substrate 11 via a plurality of bonding wires 12. An encapsulation body 13 is formed on the substrate 11 by molding and shaped as a wall structure surrounding the chip 10 and bonding wires 12; this wall-shaped encapsulation body 13 forms a cavity 14 where the chip 10 and bonding wires 12 are received without being encapsulated by the encapsulation body 13. A lid 15 is mounted and supported by the encapsulation body 13 to seal the cavity 14 and hermetically isolate the chip 10 and bonding wires 12 from the external atmosphere. The lid 15 is made of a light-permeable or transparent material to allow light to go through the lid 15 and reach the chip 10 to facilitate operation of the chip 10. This thereby provides a package structure suitable for use with the photosensitive chip.
However, the above semiconductor package may undesirably suffer significant drawbacks. The encapsulation body formed on the substrate is attached to a layer of solder mask applied over the surface of the substrate. Since adhesion between the resin compound of the encapsulation body and the solder mask is not very strong and the contact area between the encapsulation body and the substrate is relatively small, thereby delamination between the encapsulation body and the substrate may easily occur, making the reliability of the semiconductor package degrade. Moreover, since the encapsulation body is molded onto the surface of the substrate, the resin compound may easily flash to unintended area on the substrate and contaminate bond fingers formed on the substrate during molding. As a result, bonding wires cannot be perfectly bonded to the contaminated bond fingers, such that electrical connection between the chip and the substrate is damaged.
Therefore, the problem to be solved herein is to provide a semiconductor package with a photosensitive chip, which can enhance adhesion between the encapsulation body and the substrate and prevent the occurrence of resin flash over the substrate.